Ferromagnetism in Dilute Magnetic Semiconductors through Defect Engineering: Li-Doped ZnO

Abstract

We demonstrate, both theoretically and experimentally, that cation vacancy can be the origin of ferromagnetism in intrinsic dilute magnetic semiconductors. The vacancies can be controlled to tune the ferromagnetism. Using Li-doped ZnO as an example, we found that while Li itself is nonmagnetic, it generates holes in ZnO, and its presence reduces the formation energy of Zn vacancy, and thereby stabilizes the zinc vacancy. Room temperature ferromagnetism with p type conduction was observed in pulsed laser deposited ZnO:Li films with certain doping concentration and oxygen partial pressure.

Defect-trapped electrons and ferromagnetic exchange in ZnO

“…Two recent DFT studies have proposed that the V Zn vacancy is the defect responsible for ferromagnetism in ZnO films. 51,52 …”

“…One experimental and theoretical study of Li-doped ZnO found ferromagnetism in p-type ZnO. 52 The donor impurity band exchange model from Coey and coworkers 26 uses a Kondo Hamiltonian to predict a Curie temperature for transition-metal impurities in metal oxides, T C . The exchange integral J was assumed to be 1.5 eV and to favor (anti-)ferromagnetic coupling when the transition metal d band is (more)less than half-full.…”

Revealing a room temperature ferromagnetism in cadmium oxide nanoparticles: an experimental and first-principles study

“…However, defects have been recognized to play important roles in inducing RTFM in ZnO [19,20]. This explains the discrepancies often reported in experiments and offers new opportunities to search for the underlying mechanisms.…”

Room-temperature ferromagnetism via unpaired dopant electrons andp−pcoupling in carbon-doped In2O3Green1, Boukhvalov2, Kurmaev3 et al. 2012Phys. Rev. BSelf Cite351120View full textAdd to dashboardCite

“…8 Thus, it is clear that the magnetic properties of these materials are very sensitive to the constituent species and the various synthesis parameters and as such more studies are needed to fully understand the mechanisms. Here, we first employ density functional theory modeling to study the electronic structures and magnetic properties of various possible defect configurations.…”